The present invention relates in general to a variable-volume storage tank, or the like, of the type having an upright cylindrical shell and a circular roof within the cylindrical shell and adapted to float on the surface of a liquid within the shell. A circular metallic-shoe seal ring encircles and is spaced outwardly from the roof and slidably engages the shell. A hanger means interconnecting the roof and the seal ring supports the seal ring and serves to center the roof and to urge the seal ring radially outwardly against the shell. A flexible annular seal extends between the roof and the seal ring above the hanger means and has its inner periphery secured to the roof and its outer periphery secured to the seal ring. As disclosed and claimed in my aforementioned co-pending patent application, a secondary seal is located above and supplements the action of the structure just described.
Floating-roof storage tanks of the foregoing general nature are widely used in the oil industry to store variable quantities of petroleum and/or petroleum products, such as gasoline, while, at the same time, maintaining relatively vapor-tight seals between the floating roofs and the upright cylindrical shells of the tanks.